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重庆市农业碳排放时空特征分析与可解释预测

Spatiotemporal characteristics analysis and explainable prediction of agricultural carbon emissions in Chongqing

  • 摘要: 准确理解区域内的农业碳排放状态、格局及变化趋势对科学合理地制定固碳减排政策具有重要意义。该研究以重庆市为例提出一套区域农业碳排放核算、分析及预测框架,融合多源统计与遥感数据核算了2004—2023年的农业碳排放,利用时空分析方法研究农业碳排放格局特征,构建可解释的ARIMA—XGBoost预测模型研究了农业碳排放趋势。结果表明:1)重庆市年均农业碳排放约243.459万t,水稻甲烷和化肥是主要碳源,年均排放量分别达117.525万t和80.933万t。2)重庆市农业碳排放存在显著的时空差异特征,合川、梁平及垫江等区县是碳排放热点,江北、南岸及北碚等区县是碳排放冷点。3)预测至2030年,重庆市农业碳排放将由218.709万t逐渐降低至178.752万t,乡村从业人员、公路里程及农业生产总值等因素对农业碳排放变化的影响较大。研究丰富了区域碳排放评估体系,可为重庆等地的农业农村绿色低碳发展提供科学参考。

     

    Abstract: Human agricultural activities are generating substantial carbon emissions across vast regions. Accurately understanding the current status, spatiotemporal patterns, and future trends of agricultural carbon emissions is crucial for optimizing carbon sequestration and emission reduction policies and enhancing climate adaptation capabilities. However, current methods for assessing agricultural carbon emissions face an inevitable challenge of reliance on statistical data, whereby regions with incomplete statistical records may encounter greater uncertainties in carbon accounting, analysis, and forecasting, or even lack results altogether. This limits our in-depth understanding of the spatiotemporal characteristics and future trends of agricultural carbon emissions in these regions. Taking Chongqing as a case study, this study integrated multi-source agricultural data combining government statistics and remote sensing monitoring within a county-level data framework to calculate agricultural carbon emissions from 2004 to 2023. Furthermore, spatiotemporal analysis methods including slope estimation, the Mann-Kendall test, Moran's I index, and the Getis-Ord Gi* index were employed to examine change characteristics, while prediction models based on ARIMA and three machine learning methods (Support Vector Machine, Random Forest, and XGBoost) were constructed to investigate trends. The results indicate that: 1) the multi-source data integration method for agricultural carbon emission accounting is feasible and reliable, yielding an average annual agricultural carbon emission of approximately 2.435 million tons for Chongqing. This result correlates significantly with accounting based on traditional statistical data (R2=0.932, p<0.05), compensating for missing county-level statistical data and demonstrating higher stability. 2) Significant source and regional differences exist in Chongqing's agricultural carbon emissions. Methane emissions from rice cultivation and carbon emissions from fertilizer use are the primary sources, with average annual emissions reaching 1.175 million tons and 0.809 million tons, respectively. The spatial agglomeration of agricultural carbon emissions in Chongqing has intensified year by year, with the global Moran's I index reaching 0.695, 0.615, and 0.64 in 2017, 2021, and 2023, respectively. Districts such as Wanzhou, Liangping, and Zhongxian were identified as emission hotspots, with average annual agricultural carbon emissions of approximately 0.106, 0.105 and 0.089 million tons, respectively; whereas Beibei, Yubei, and Jiangbei were identified as emission cold spots, with average annual emissions of approximately 0.03, 0.051 and 0.01 million tons, respectively. 3) The interpretable ARIMA-XGBoost prediction model performed well on an independent test set (R2=0.936) and revealed that Chongqing's agricultural carbon emissions will shift from a general stable state to a more widespread downward trend. Total emissions are projected to gradually decrease from 2.187 million tons to 1.788 million tons between 2024 and 2030. Factors such as rural employees, highway mileage and gross agricultural product exert a more significant influence on changes in agricultural carbon emissions, yet the spatially differentiated distribution across counties remains largely unchanged. This study highlights the advantages of information complementarity and reliability offered by the multi-source data integration method for agricultural carbon emission accounting, analysis, and forecasting, thereby enhancing the regional agricultural carbon emission assessment framework. It provides a scientific foundation for formulating carbon sequestration and emission reduction policies in Chongqing's agricultural and rural sectors and serves as a valuable methodological reference for selecting green and low-carbon development strategies in similar regions.

     

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